Off-chip tap interface control with instruction register, multiplexer and buffer

ABSTRACT

An IC includes an IEEE 1149.1 standard test access port (TAP) interface and an additional Off-Chip TAP interface. The Off-Chip TAP interface connects to the TAP of another IC. The Off Chip TAP interface can be selected by a TAP Linking Module on the IC.

RELATED PATENTS/APPLICATIONS

This application is a divisional of application Ser. No. 14/231,967,filed Apr. 1, 2014, now U.S. Pat. No. 9,188,639, issued Nov. 17, 2015;

Which was a divisional of application Ser. No. 13/765,194, filed Feb.12, 2013, now U.S. Pat. No. 8,726,110, granted May 13, 2014;

Which was a divisional of application Ser. No. 13/370,521, filed Feb.10, 2012, now U.S. Pat. No. 8,402,330, granted Mar. 19, 2013;

Which was a divisional of application Ser. No. 13/246,251, filed Sep.27, 2011, now U.S. Pat. No. 8,140,926, granted Mar. 20, 2012;

Which was a divisional of application Ser. No. 12/899,992, filed Oct. 7,2010, now U.S. Pat. No. 8,055,967, granted Nov. 8, 2011;

Which was a divisional of application Ser. No. 12/642,222, filed Dec.18, 2009, Now U.S. Pat. No. 7,831,878, granted Nov. 9, 2010;

Which was a divisional of application Ser. No. 12/021,582, filed Jan.29, 2008, now U.S. Pat. No. 7,661,049, granted Feb. 9, 2010;

Which was a divisional of application Ser. No. 10/928,239, filed Aug.27, 2004, now U.S. Pat. No. 7,346,821, granted Mar. 18, 2008;

Which claims priority under 35 USC 119(e)(1) of provisional applicationNo. 60/498,636, filed Aug. 28, 2003.

This application is related to U.S. Pat. Nos. 6,073,254, 6,324,662 and7,058,862, as well as Patent Publication 2002/0,049,928, all of whichare completely incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

This invention relates in general to integrated circuits that include anIEEE 1149.1 standard test access port (TAP) interface for providingaccess to on chip test, debug, emulation, and in-system programmingoperations. In particular this invention relates to including anadditional Off Chip TAP interface. The additional Off Chip TAP interfaceis used for accessing the JTAG port of another IC that is not externallyconnected.

BACKGROUND OF THE INVENTION

FIG. 1A illustrates the architecture of a conventional 1149.1 TAPcircuit domain. The TAP domain includes a TAP controller, instructionregister, set of data register including; (1) an internal scan register,(2) an in-circuit emulation (ICE) register, (3) an in-system programming(ISP) register, (4) a boundary scan register, and (5) a bypass register.Of the data registers, the boundary scan register and bypass registerare defined by the IEEE 1149.1 standard. The other shown data registersare not defined by 1149.1, but can exist as data registers within theTAP domain. The TAP controller responds to the Test Clock (TCK) and TestMode Select (TMS) signal inputs to coordinate serial communicationthrough either the instruction register from Test Data In (TDI) signalto Test Data Out (TDO) signal, or through a selected one of the dataregisters from TDI to TDO. The Test Reset (TRST) signal input is used toinitialize the TAP domain to a known state. The operation of the TAPdomain is well known

FIG. 1B illustrates an IC or intellectual property core circuitincorporating the TAP domain and its TDI, TDO, TMS, TCK, and TRSTinterface. A core is a complete circuit function that is embedded withinthe substrate of an IC, such as a DSP or CPU core.

FIGS. 1C-1F illustrate the association between each of the dataregisters of FIG. 1A and the functional target circuit they connect toand access.

FIG. 2 illustrates the state diagram of the TAP controller of FIG. 1A.The TAP controller is clocked by the TCK input and transitions throughthe states of FIG. 2 in response to the TMS input. As seen in FIG. 2,the TAP controller state diagram consists of four key state operations,(1) a Reset/RunTest Idle state operation where the TAP controller goesto either enter a reset state, a run test state, or an idle state, (2) aData or Instruction Scan Select state operation the TAP controller maytransition through to select a data register (DR) or instructionregister (IR) scan operation, or return to the reset state, (3) a DataRegister Scan Protocol state operation where the TAP controller goeswhen it communicates to a selected data register, and (4) an InstructionRegister Scan Protocol state operation where the TAP controller goeswhen it communicates to the instruction register. The operation of theTAP controller is well known.

FIG. 3 illustrates an example arrangement for connecting multiple TAPdomains within an IC. Each TAP domain in FIG. 3 is similar to that shownand described in regard to FIG. 1A. While only one IC TAP domain existsin an IC, any number of core TAP domains (1-N) may exist within an IC.As seen in FIG. 3, the IC TAP domain and Core 1-N TAP domains aredaisychained between the IC's TDI and TDO pins. All TAP domains areconnected to the IC's TMS, TCK, and TRST signals and operate accordingto the state diagram of FIG. 2. During instruction scan operations,instructions are shifted into each TAP domain instruction register. Onedrawback of the TAP domain arrangement of FIG. 3 is that it does notcomply with the IEEE 1149.1 standard, since, according to the rules ofthat standard, only the ICs TAP domain should be present between TDI andTDO when the IC is initially powered up. A second drawback of the TAPdomain arrangement of FIG. 3 is that it may lead to unnecessarilycomplex access for testing, in-circuit emulation, and/or in-circuitprogramming functions associated with ones of the individual TAPdomains.

For example, if scan testing is required on circuitry associated withthe Core 1 TAP domain, each of the scan frames of the test pattern setdeveloped for testing the Core 1 circuitry must be modified from theiroriginal form. The modification involves adding leading and trailing bitfields to each scan frame such that the instruction and data registersof the leading and trailing TAP domains become an integral part of thetest pattern set of Core 1. Serial patterns developed for in-circuitemulation and/or in-circuit programming of circuitry associated with theTAP domain of Core 1 must be similarly modified. To overcome these andother drawbacks of the TAP arrangement of FIG. 3, the TAP arrangement ofFIG. 4 was developed.

FIG. 4 illustrates a preferred structure for connecting multiple TAPdomains within an IC according to U.S. Pat. No. 7,058,862. The structureincludes input and output linking circuitry for connecting any one ormore TAP domains to the IC's TDI, TDO, TMS, TCK and TRST pins or bondpads, and a TAP Linking Module (TLM) circuit for providing the controlto operate the input and output linking circuitry. The combination ofthe input and output linking circuitry and TLM are hereafter referred toas the TLM architecture (TLMA). The concept of input and output linkingcircuitry and use of a TLM circuit to control the input and outputlinking circuitry was first disclosed in the referenced U.S. Pat. No.7,058,862. The concept of the use of a TLM circuit was first disclosedin the referenced U.S. Pat. No. 6,073,254.

The input linking circuitry receives as input; (1) the TDI, TMS, TCK,and TRST signals on pins or bond pads of the IC, (2) the TDO outputsfrom the IC TAP (ICT) domain (TDO_(JCT)), the Core 1 TAP (C1T) domain(TDO_(C1T)), and the Core N TAP (CNT) domain (TDO_(CNT)), and (3) TAPlink control input from the TLM. The TCK and TRST inputs pass unopposedthrough the input linking circuitry to be input to each TAP domain. TheTMS input to the input linking circuitry is gated within the inputlinking circuitry such that each TAP domain receives a uniquely gatedTMS output signal. As seen in FIG. 4, the IC TAP domain receives a gatedTMS_(ICT) signal, the Core 1 TAP domain receives a gated TMS_(C1T)signal, and the Core N TAP domain receives a gated TMS_(CNT) signal.Example circuitry for providing the gated TMS_(ICT), TMS_(C1T), andTMS_(CNT) signals is shown in FIG. 5. In FIG. 5, the ENA_(ICT),ENA_(C1T), and ENA_(CNT) signals used to gate the TMS_(ICT), TMS_(C1T),and TMS_(CNT) signals, respectively, come from the TLM via the TAP linkcontrol bus.

From FIG. 5 it is seen that TMS_(CNT) can be connected to TMS to enablethe Core N TAP domain or be gated low to disable the Core N TAP domain,TMS_(C1T) can be connected to TMS to enable the Core 1 TAP domain or begated low to disable the Core 1 TAP domain, and TMS_(ICT) can beconnected to TMS to enable the IC TAP domain or be gated low to disablethe IC TAP domain. When a TAP domain TMS input (TMS_(CNT), TMS_(C1T),TMS_(ICT)) is gated low, the TAP domain is disabled by forcing it toenter the Run Test/Idle state of FIG. 2. A disabled TAP domain willremain in the Run Test/Idle state until it is again enabled by couplingit to the IC's TMS pin input as mentioned above. These methods ofenabling TAP domains from the Run Test/Idle state and disabling TAPdomains to the Run Test/Idle state was first disclosed in referencedU.S. Pat. No. 6,073,254.

The TDI, TDO_(CNT), TDO_(C1T), and TDO_(ICT) inputs to the input linkingcircuitry are multiplexed by circuitry within the input linkingcircuitry such that each TAP domain receives a uniquely selected TDIinput signal. As seen in FIG. 4, the IC TAP domain receives a TDI_(JCT)input signal, the Core 1 TAP domain receives a TDI_(C1T) input signal,and the Core N TAP domain receives a TDI_(CNT) input signal. Examplecircuitry for providing the TDI_(JCT), TDI_(C1T), and TDI_(CNT) inputsignals is shown in FIG. 6.

In FIG. 6, the SELTDI_(ICT), SELTDI_(C1T), and SELTDI_(CNT) controlsignals used to select the source of the TDI_(JCT), TDI_(C1T), andTDI_(CNT) input signals, respectively, come from the TLM via the TAPlink control bus. From FIG. 6 it is seen that TDI_(CNT) can beselectively connected to TDI, TDO_(C1T), or TDO_(ICT), TDI_(C1T) can beselectively connected to TDI, TDO_(CNT), or TDO_(ICT), and TDI_(JCT) canbe selectively connected to TDI, TDO_(CNT), or TDO_(C1T).

The output linking circuitry receives as input; (1) the TDO_(CNT) outputfrom the Core N TAP domain, the TDO_(C1T) output from the Core 1 TAPdomain, the TDO_(ICT) output from the IC TAP domain, and TAP linkcontrol input from the TLM. As seen in FIG. 4, the output linkingcircuitry outputs a selected one of the TDO_(CNT), TDO_(C1T), andTDO_(ICT) input signals to the TLM via the output linking circuitry TDOoutput. Example circuitry for providing the multiplexing of theTDO_(ICT), TDO_(C1T), and TDO_(CNT) signals to the TDO output is shownin FIG. 7.

In FIG. 7, the SELTDO control input used to switch the TDO_(ICT),TDO_(C1T), or TDO_(CNT) signals to TDO come from the TLM via the TAPlink control bus. From FIG. 7 it is seen that any one of the TDO_(CNT),TDO_(C1T), and TDO_(ICT) signals can be selected as the input source tothe TLM.

The TLM circuit receives as input the TDO output from the output linkingcircuitry and the TMS, TCK, and TRST IC input pin signals. The TLMcircuit outputs to the IC's TDO output pin. From inspection, it is seenthat the TLM lies in series with the one or more TAP domains selected bythe input and output linking circuitry.

As described above, the TLM's TAP link control bus is used to controlthe input and output connection circuitry to form desired connections toone or more TAP domains so that the one of more TAP domains may beaccessed via the IC's TDI, TDO, TMS, TCK, and TRST pins. The TAP linkcontrol bus signals are output from the TLM during the Update-IR stateof the IEEE TAP controller state diagram of FIG. 2.

FIG. 8A illustrates in detail the structure of the TLM. The TLM consistsof a TAP controller, instruction register, multiplexer, and 3-state TDOoutput buffer. The TAP controller is connected to the TMS, TCK and TRSTsignals. The TDI input is connected to the serial input (I) of theinstruction register and to a first input of the multiplexer. The serialoutput (O) of the instruction register is connected to the second inputof the multiplexer. The parallel output of the instruction register isconnected to the TAP link control bus of FIG. 4. The output of themultiplexer is connected to the input of the 3-state buffer. The outputof the 3-state buffer is connected to the IC TDO output pin. The TAPcontroller outputs control (C) to the instruction register, multiplexer,and 3-state TDO output buffer. The TAP controller responds to TMS andTCK input as previously described in regard to FIGS. 1A and 2. Duringinstruction scan operations, the TAP controller enables the 3-state TDObuffer and shifts data through the instruction register from TDI to TDO.During data scan operations, the TAP controller enables the 3-state TDObuffer and forms a connection, via the multiplexer, between TDI and TDO.

FIG. 8B illustrates the instruction register in more detail. Theinstruction register consists of a shift register, TAP link decodelogic, and update register. The shift register has a serial input (I), aserial output (O), a control (C) inputs, a parallel output, and aparallel input. The parallel input is provided for capturing fixed logic0 and 1 data bits into the first two bit positions shifted out on TDOduring instruction scan operations, which is a requirement of the IEEE1149.1 standard. The parallel output from the instruction register isinput to TAP link decode logic. The parallel output from the TAP linkdecode logic is input to the update register. The parallel output of theupdate register is the TAP link control bus input to the input andoutput linking circuitry. During the Capture-IR state of FIG. 2, theshift register captures data (0 & 1) on the parallel input, During theShift-IR state of FIG. 2, the shift register shifts data from TDI (I) toTDO (O). During the Update-IR state of FIG. 2, the update register loadsthe parallel input from the TAP link decode logic and outputs the loadeddata onto the TAP link control bus.

FIG. 9 illustrates various possible link arrangements Link0-Link6 of TAPdomain connections during 1149.1 instruction scan operations using theTLMA. Since during instruction scan operations, the TLM's instructionregister is physically present and in series with the connected TAPdomain(s) instruction register(s), the instruction scan frame for eachlink arrangement will be augmented to include the TLM's instructionregister bits. The concept of augmenting the length of TAP domaininstruction registers with a TLM's instruction register was firstdisclosed in referenced pending patent application TI-27596. In thisexample, the TLM's instruction shift register of FIG. 8B is 3 bits longand the 3 bit instructions (000-110) are decoded by the TAP link decodelogic of FIG. 8B to uniquely select a different TAP domain connectionlink arrangement between the ICs TDI and TDO pins. Shifting in thefollowing 3 bit TLM instructions and updating them from the TLM to beinput to the input and output linking circuitry will cause the followingTAP domain link connections to be formed.

A Link0 “000” instruction shifted into and updated from the TLMinstruction register will cause the IC TAP domain to be enabled andconnected in series with the TLM between the TDI and TDO IC pins.

A Link1 “001” instruction shifted into and updated from the TLMinstruction register will cause the IC TAP domain and the Core 1 TAPDomain to be enabled and connected in series with the TLM between theTDI and TDO IC pins.

A Link2 “010” instruction shifted into and updated from the TLMinstruction register will cause the IC TAP domain and the Core N TAPDomain to be enabled and connected in series with the TLM between theTDI and TDO IC pins.

A Link3 “011” instruction shifted into and updated from the TLMinstruction register will cause the IC TAP domain, the Core 1 TAPDomain, and the Core N TAP domain to be enabled and connected in serieswith the TLM between the TDI and TDO IC pins.

A Link4 “100” instruction shifted into and updated from the TLMinstruction register will cause the Core 1 TAP Domain to be enabled andconnected in series with the TLM between the TDI and TDO IC pins.

A Link5″101″ instruction shifted into and updated from the TLMinstruction register will cause the Core 1 TAP Domain and Core N TAPdomain to be enabled and connected in series with the TLM between theTDI and TDO IC pins.

A Link6 “110” instruction shifted into and updated from the TLMinstruction register will cause the Core N TAP Domain to be enabled andconnected in series with the TLM between the TDI and TDO IC pins.

At power up of the IC, the TLM 3-bit instruction shall be initialized to“000” to allow the IC TAP domain Link0 arrangement to be enabled andcoupled between TDI and TDO. This complies with the IC power uprequirement established in the IEEE 1149.1 standard. The process ofpowering up a multiple TAP domain IC to where only the IC TAP domain isenabled and selected between the IC's TDI and TDO pins was firstdisclosed in referenced patent application TI-23727. Following power up,an instruction scan operation can be performed to shift instruction datathrough the IC TAP domain and the serially connected TLM to load a newIC TAP domain instruction and to load a new 3 bit link instruction intothe TLM. If the power up IC TAP domain Link0 arrangement is to remain ineffect between TDI and TDO, the 3 bit “000” TLM instruction of FIG. 9will be re-loaded into the TLM instruction register during the abovementioned instruction scan operation. However, if a new TAP domain linkarrangement is desired between TDI and TDO, a different 3 bit TLM linkinstruction will be loaded into the TLM instruction register during theabove mentioned instruction register scan operation.

FIG. 10 is provided to illustrate that during 1149.1 data scanoperations the TLM is configured, as described in regard to FIG. 8A, tosimply form a connection path between the output of the selected TAPdomain link arrangement Link0-Link6 and the IC's TDO pin. Thus the TLMdoes not add bits to 1149.1 data scan operations as it does for 1149.1instruction scan operations.

SUMMARY OF THE INVENTION

In accordance with the present invention, the TLM architecture providesan Off-Chip TAP interface to external the IC that can be selected in alink arrangement. The Off-Chip TAP interface can be used to select theIEEE 1149.1 TAP interface of another, separate IC to be included in alink arrangement. The improvement therefore provides for the TLMarchitecture of an IC to be used not only for selecting TAP domainsresiding in the IC but also used for selecting TAP domains residing onother ICs. For example, the TAP domain of an external IC/die may beselected.

The other, separate IC included in the link arrangement from theOff-Chip TAP interface may include its own TLM architecture. The other,separate IC included in the link arrangement from the Off-Chip TAPinterface may further include its own Off-Chip TAP interface to the IEEE1149.1 TAP interface of further ICs. This provides for a hierarchyarrangement of TAP interfaces.

Any number of Off-Chip TAP interfaces may be provided on one IC.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a conventional art IEEE 1149.1 (JTAG) architectureas it could be implemented within an IC or core circuit.

FIG. 1B illustrates the conventional art substrate of an IC or corecircuit including the JTAG architecture and interface.

FIG. 1C illustrates a conventional art JTAG accessible internal scanpath coupled to logic circuitry.

FIG. 1D illustrates a conventional art JTAG accessible in-circuitemulation register coupled to emulation circuitry.

FIG. 1E illustrates a conventional art JTAG accessible in-systemprogramming register coupled to in-system programming circuitry.

FIG. 1F illustrates a conventional art JTAG accessible boundary scanregister coupled to input and output circuitry.

FIG. 2 illustrates the conventional art state diagram of the JTAG TAPcontroller.

FIG. 3 illustrates an IC containing conventional art TAP domainsdaisy-chained between the ICs TDI and TDO pins.

FIG. 4 illustrates a conventional art TAP Linking Module (TLM)Architecture implemented within an IC.

FIG. 5 illustrates conventional art TMS gating circuitry that could beused in the input linking circuitry of the FIG. 4 TLM architecture.

FIG. 6 illustrates conventional art TDI multiplexing circuitry thatcould be used in the input linking circuitry of the FIG. 4 TLMarchitecture.

FIG. 7 illustrates conventional art TDO multiplexing circuitry thatcould be used in the output linking circuitry of the FIG. 4 TLMarchitecture.

FIG. 8A illustrates conventional art TLM circuitry that could be used inthe FIG. 4 TLM architecture.

FIG. 8B illustrates an instruction register that could be used in theconventional art TLM circuitry of FIG. 8A.

FIG. 9 illustrates some possible conventional art TAP domain linkingarrangements of the TLM architecture of FIG. 4 as they would appearduring JTAG instruction scan operations.

FIG. 10 illustrates the conventional art TAP domain linking arrangementsof FIG. 9 as they would appear during JTAG data scan operations.

FIG. 11A illustrates the TLM architecture of FIG. 4 improved to includethe Off-Chip TAP (OCT) interface of the present invention.

FIG. 11B illustrates the OCT interface being coupled to the JTAGinterface of another IC/die.

FIG. 12 illustrates the TMS gating circuitry of FIG. 5 including anadditional TMS gate for controlling access to the OCT interface.

FIG. 13 illustrates the TDI multiplexing circuitry of FIG. 6 includingan additional TDI multiplexer for input to OCT interface and the othermultiplexers being equipped with an additional input for receiving TDOinput from the OCT interface.

FIG. 14 illustrates the TDO multiplexer circuitry of FIG. 7 beingequipped with an additional input for receiving the TDO output from theOCT interface.

FIG. 15 illustrates some possible TAP domain linking arrangements fromthe TLM architecture of FIG. 11A as they would appear during JTAGinstruction scan operations.

FIG. 16 illustrates the TAP domain linking arrangements of FIG. 14 asthey would appear during JTAG data scan operations.

FIGS. 17A-17O illustrate various TAP domain link arrangements betweentwo Die on a substrate, each Die including the improved TLM architectureof FIG. 11A.

FIG. 18 illustrates a more complex arrangement of Die on substrate, eachDie including the improved TLM architecture of FIG. 11A.

FIG. 19 illustrates two substrates serially daisy-chained to a JTAGcontroller, each substrate including two Die each implementing theimproved TLM architecture of FIG. 11A.

FIG. 20 illustrates the improved TLM architecture whereby the positionof the TLM circuit is moved such that it exists on the serial path nextto the IC's TDI input pin instead of on the serial path next to the IC'sTDO pin as illustrated in FIG. 11A.

FIG. 21 illustrates a functional IC that includes the conventional JTAGport interface and the OCT interface of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 11A illustrates the improvement to the TLM architecture of FIG. 4.The improvement is the addition of an Off-Chip Tap (OCT) interface 1106.The OCT interface can be selected between the ICs TDI and TDO pins, viathe TLM's TAP Link Control bus, exactly as the IC and core TAP domainswere described being selected. Once selected, the OCT interface canserve as a master TAP interface to a slave TAP interface (i.e. aconventional 1149.1 TAP interface) on another IC. Thus an IC having theTLM architecture improvement shown in FIG. 11A would have theconventional 1149.1 TAP interface 1102 plus the selectable OCT interface1106 for mastering the TAP interface of another IC or ICs 1108. Whileone OCT interface 1106 is shown in FIG. 11A, any number of OCTinterfaces may be provided.

FIG. 11B illustrates the OCT interface 1106 being coupled 1110 to a TAPinterface of another IC 1108. As seen in FIG. 11B, the OCT interfaceconsists of buffers which couple the TDI_(OCT), TCK, TMS_(OCT),TDO_(OCT), and TRST TLM architecture signals up to TDO, TCK, TMS, TDI,and TRST pads 1104, respectively, of the IC in which the TLMarchitecture resides. The TDO, TCK, TMS, TDI and TRST pads 1104 can becoupled to the TDI, TCK, TMS, TDO and TRST pads of the other IC 1108,via connections 1110, to provide access the TAP domain of the other IC1108. The TAP domain of the other IC could be similar to that shown inFIG. 1A.

FIGS. 12-14 illustrate the changes required to the Input and Outputlinking circuitry of FIGS. 5-7, respectively, to add the OCT interfaceof FIG. 11A. As seen in FIG. 12, an additional AND gate 1202 is added toprovide gating on and off the TMS input (TMS_(OCT)) of the OCTinterface. As seen in FIG. 13, an additional multiplexer 1302 isprovided for selecting the TDI input (TDI_(OCT)) of the OCT interface,and the other multiplexers are provided with an additional input forreceiving the TDO output (TDO_(OCT)) of the OCT interface. As seen inFIG. 14, an input is added to the output multiplexer to receive the TDOoutput (TDO_(OCT)) of the OCT. Additionally, control signals are addedto the TLM's TAP Link Control bus to provide for controlling the addedTMS_(OCT) AND gate, the additional TDI_(OCT) multiplexer, and theadditional TDO_(OCT) input to the multiplexers.

FIG. 15 illustrates examples of the possible TAP Link arrangements(Link0-Link13) of the TLM architecture of FIG. 11A during TAPinstruction register scan operations. The link arrangements includethose previously shown in FIG. 9, plus additional link arrangements thatinclude the OCT interface. As seen, there are two powerup/reset optionsfor the default TAP link, Link0 and Link7. The Link0 (option 1) selectsonly the IC's TAP in the link, whereas Link7 (option 2) selects the IC'sTAP plus the OCT interface in the link. An example of why option 2 maybe necessary is shown in example F of FIG. 17.

FIG. 16 is provided to simply show, as did FIG. 9, that the TLM istransparent during TAP data register scan operations.

FIGS. 17A-17O show examples of various TAP Link arrangements between twodie (Die 1 and 2) located on a common substrate. While each Die 1 and 2is shown including the improved TLM architecture (TLMA) of FIG. 16 itshould be understood that only Die 1 of each example requires the TLMarchitecture of FIG. 16 to provide access to Die 2. Die 2 of eachexample could simply have a JTAG architecture as shown in FIG. 1A. Ineach example, the conventional TAP interface 1702 of Die 1 (TDI, TCK,TMS, TRST, and TDO) is the TLMA interface of Die 1 and is coupled to aJTAG bus controller, such as a tester, debugger, emulator, or othercontroller. Also in each example, the OCT interface 1704 of Die 1 (TDI,TCK, TMS, TRST and TDI) is coupled to the conventional TAP interface1706 of Die 2 (TDI, TCK, TMS, TRST and TDI) which is the TLMA interfaceof Die 2.

In example A, only the IC TAP of Die 1 is included in the link to theJTAG controller. In example B, only the Core N TAP is included in thelink to the JTAG controller. In example C, only the Core 1 TAP isincluded in the link to the JTAG controller. In example D, the Core 1and Core N TAPs are included in the link to the JTAG controller. Inexample E, all TAPs of Die 1 are included in the Link to the JTAGcontroller.

In example F, the IC TAPs of Die 1 and 2 are included in the Link to theJTAG controller, the IC TAP of Die 2 being accessed via the OCTinterface of Die 1. The Link of Example F would be selected to allowperforming JTAG Extest interconnect testing on both Die 1 and Die 2. Asmentioned in regard to option 2 of FIG. 16, the link arrangement ofexample F may be selected as the powerup/reset link to allow the IC TAPsof both Die 1 and 2 to be accessed for interconnect testing.

In example G, the TAPs of Die 1 are all bypassed while the IC TAP of Die2 is included in the link to the JTAG controller via the OCT of Die 1.In this arrangement, the TAP link of Die 1 would be as shown in Link13of FIGS. 15 and 16. Examples H through L similarly bypass the Die 1 TAPsto access the TAPs of Die 2 via the OCT. Example M through O illustratesvarious links that include TAPs of both Die 1 and Die 2. Examples L andO illustrate that the OCT of Die 2 could be used if necessary to link toTAP interfaces of other Die.

FIG. 18 illustrates an example of a more complex Die on Substratearrangement whereby the flexibility of the improved TLM architecture canbe further seen. The TLMA interface 1802 of Die 1 serves as the Diecoupled to the JTAG controller, as it did in the previous examples. Die1 also serves as the TAP access point, via its OCT 1804, todaisy-chained TLMA interfaces 1806 and 1808 of Die 2 and 3. Die 2 andDie 3 serve as further TAP access points, via their OCTs 1810 and 1812,to TLMAs 1814 and 1816 of Die 4 and 5, respectively. By dotted linearrows it is seen that any one or more TAP domains of each Die 1-5 maybe selected and linked for access via the JTAG controller connection toDie 1. Further, bypassing of Die 1, as in examples G through L allowsdirect access to Die 2 and 3. Die 2 and 3 can be similarly bypassed toprovide direct access to Die 4 and 5.

FIG. 19 illustrates two substrates 1902 and 1904 each with two die thatinclude the improved TLM architecture of FIG. 11A. Substrate 1902includes a die labeled Die 1:1 and a die labeled Die 1:2. Substrate 1904includes a die labeled Die 2:1 and a die labeled Die 2:2. The TLMAinterface 1906 of Die 1:1 is daisy-chained with the TLMA interface 1914of Die 2:1. The daisy-chained path is coupled to a JTAG controller. TheTLMA interface 1910 of Die 1:2 is coupled to the OCT interface 1908 ofDie 1:1. The TLMA interface 1918 of Die 2:2 is coupled to the OCTinterface 1916 of Die 2:1. The importance of FIG. 19 is the showing of aserial access approach whereby the JTAG controller may access TAPdomains vertically as well as horizontally. The Die labeling is donesuch that the left number indicates the horizontal position of the Die'ssubstrate on the daisy-chained path and the right number indicates thevertical position of the Die on the substrate.

In a first example, the JTAG controller may horizontally access TAPdomains of only Die 1:1 and 2:1 in the daisy-chain arrangement withoutaccessing the TAP domain of vertically accessible Die 1:2 and 2:2. In asecond example, the JTAG controller may vertically access the TAPdomains of Die 1:2, via the OCT of Die 1:1, and include those TAPdomains in with the daisy-chained horizontal access of TAP domains inDie 1:1 and 2:1. In a third example, the JTAG controller may verticallyaccess the TAP domains of Die 1:2 via the OCT of Die 1:1, the TAPdomains of Die 2:2 via the OCT of Die 2:1, and include those TAP domainsin with the daisy-chained horizontal access of TAP domains in Die 1:1and 2:1. In a forth example, the JTAG controller may bypass (as shown inFIGS. 17J-17I) the TAP domains of Die 1:1 and 2:1 to vertically accessthe TAP domains of Die 1:2 and 2:2 such that only the TAP domains of Die1:2 and 2:2 are included in the horizontal daisy-chain path to the JTAGcontroller. As can be seen, access to additional vertical Die ispossible using the OCT interfaces 1912 and 1920 of Die 1:2 and 2:2.

FIG. 20 is provided to indicate that the TLM can be positioned at thebeginning of the IC's TDI to TDO serial path instead of at the ending asshown in FIG. 11A, if desired. The TLM circuit would operate aspreviously described to control the input and output linking circuitry.The only difference would be that the TLM's instruction shift registerwould no longer need to capture the JTAG required 0 and 1 bits shown inFIG. 8B, since those 0 and 1 bits would be provided during instructionscan operations to the IC's TDO by the selected TAP domain(s)instruction register. The leading position of the TLM in FIG. 19 wouldalter the TAP link arrangement examples of FIGS. 15 and 16 to the extentthat the TLM would be shown existing at the beginning of the linked TAPdomains (i.e. closes to the TDI pin) instead of at the ending of thelinked TAP domains (i.e. closes to the TDO pin).

FIG. 21 illustrates an IC including the present invention. The IC hasfunctional inputs and outputs and functional circuitry responsivethereto. The IC has a conventional primary JTAG port (i.e. TLMAinterface of the present invention) and a secondary JTAG port (i.e. OCTinterface of the present invention). While a detail description has beengiven of how the TLM architecture can be improved to include thesecondary JTAG port (OCT) of FIG. 21, there may bealternative/derivative approaches that could be envisioned to couple aprimary JTAG port of a functional IC to a secondary port of the samefunctional IC. These other approaches would be inspired by the teachingsprovided by the present invention. To the extent that the presentinvention has provided an original teaching of at least one preferredway of doing this, the invention deserves claims that would broadlycover a functional IC that includes a conventional primary JTAG port forcoupling to a JTAG controller and a secondary JTAG port for coupling toanother primary JTAG port of another IC.

What is claimed is:
 1. An integrated circuit comprising: A. a substrate;B. a TDI input pad, a TCK input pad, a TMS input pad, and a TDO outputpad, all formed on the substrate; C. an IC TAP domain formed on thesubstrate, the IC TAP domain having an IC TDI input lead, an IC TCKinput lead, an IC TMS input lead, and an IC TDO output lead; D. a coreTAP domain formed on the substrate, the core TAP domain having a coreTDI input lead, a core TCK input lead, a core TMS input lead, and a coreTDO output lead; E. an off-chip TAP interface formed on the substrate,the off-chip TAP interface having an interface TDI input lead, anoff-chip TDO output lead coupled to the interface TDI input lead, aninterface TCK input lead, an off-chip TCK output lead coupled to theinterface TCK input lead, an interface TMS input lead, an off-chip TMSoutput lead coupled to the interface TMS input lead, an interface TDOoutput lead, and an off-chip TDI input lead coupled to the interface TDOoutput lead; F. input linking circuitry formed on the substrate, theinput linking circuitry coupling the TDI input pad to one of the IC TDIinput lead, the core TDI input lead, and the interface TDI input lead,and the input linking circuitry coupling the TMS input pad to the TMSinput lead of the selected IC TAP domain, the core TAP domain, and theTAP interface in response to control signals on control input leads; G.output linking circuitry formed on the substrate, the output linkingcircuitry selectively coupling one of the IC TDO output lead, the coreTDO output lead, and the interface TDO output lead to the TDO output padin response to control signals on control input leads; and H linkingcontrol circuitry formed on the substrate and connected in seriesbetween the TDI input pad and the TDO output pad, the linking controlcircuitry including an instruction register having a TDI input coupledto the TDI input pad, control output leads connected to the controlinput leads of the input linking circuitry and the output linkingcircuitry, and an output, a multiplexer having a TDI input coupled tothe TDI input pad, a register input coupled to the output of theinstruction register, and an output, and a buffer having an inputcoupled to the output of the multiplexer and an output coupled to theTDO output pad.
 2. The integrated circuit of claim 1 in which the IC TAPdomain includes boundary scan circuitry coupled to I/O circuitry.
 3. Theintegrated circuit of claim 1 in which the IC TAP domain includesboundary scan circuitry coupled to I/O circuitry, and the core TAPdomain includes core circuitry separate from the I/O circuitry and theIC TAP domain.
 4. The integrated circuit of claim 1 in which theoff-chip TAP interface includes circuitry separate from the IC TAPdomain and the core TAP domain.
 5. The integrated circuit of claim 1 inwhich the linking control circuitry is connected between the TDI inputpad and the input linking circuitry.
 6. The integrated circuit of claim1 in which the linking control circuitry is connected between the outputlinking circuitry and the TDO output pad.
 7. The integrated circuit ofclaim 1 in which the input linking circuitry includes multiplexercircuitry having inputs connected to the TDI input pad, the IC TDOoutput lead, the core TDO output lead, and the interface TDO outputlead, and having an output coupled to the IC TDI input lead, an outputcoupled to the core TDI input lead, and an output coupled to theinterface TDI input lead.
 8. The integrated circuit of claim 1 in whichthe input linking circuitry includes gating circuitry selectivelyconnecting the first TMS input pad to each of the TAP domain, the coreTAP domain, and the TAP interface.